(a) Field of the Invention
The invention relates to a joint damping device for use in an articulated omnibus whose front vehicle is connected with the rear vehicle by a live ring as a rotary joint, there being at least one hydraulic cylinder or shock absorber between the front and rear vehicle.
(b) Background and Prior Art
Articulated omnibuses having a rear engine and transmission on the axle of the rear vehicle--so-called pusher systems--require an anti-jackknifing device for winter operation. Furthermore in the case of such designs of articulated buses a damping means is required at the joint for reasons of stability owing to the unusual weight distribution, more especially at high speeds of travel.
Articulation angle control systems for articulated buses in the form of articulation locking devices and articulation dampers have been proposed in a large number of different designs. However, presently it is only necessary to take into account the three systems which are used in practice. Thus one form (see the German specification, DE-OS 2,420,203) of articulation locking device uses two hydraulic cylinders located between the front and rear vehicles whose actuation to lock the articulation is achieved by a system with two potentiometers, an electronic circuit and a hydraulic control system and the locking of the articulation is at a given angle in response to a comparison between the steering angle and the articulation angle, other parameters, i.e. speed of travel, articulation rate and articulation acceleration being taken into account as well. In accordance with another design (see German specification, DE-OS, 3,623,655) there is a double acting hydraulic cylinder arranged in the front vehicle transversely of the direction of travel so that the longitudinally moving cylindrical casing is connected with two steel cords which are trained about a rocking segment and are connected with the part of the live ring connected to the rear vehicle. Control is such as to respond to the rate of articulation using two potentiometers, an electronic circuit and a hydraulic control system. The system may also be set manually so that the damping action is constant.
The hydraulic, electronic and electric controlling and monitoring devices required for the known systems make them very elaborate. Apart from the liability to failure in the numerous electrical connections and components installed, there is also the necessity of a slow and thus expensive setting and matching procedure, which may only be performed by trained staff. Articulated buses fitted with such systems are very often not suitable for export. There is thus a demand for simple, straightforward anti-jackknifing systems, which if required may be serviced or repaired by staff of average training.
One articulation damping device (see the German specification 2,748,713) has been proposed which is able to operate without electronic control elements, and it has means for automatically adapting it to the road conditions. The cylinders arranged between the primary vehicle and the secondary one are in the form of biased damping cylinders, which act with a stabilizing effect on the articulated vehicle when it takes a corner.